Dr MINH HUAN DANG1,2, PEEMAPAT PRAKONGTHAM1, MARK HOGARTH3, DIETER E JENNE4, LANI SHOCHET1,2, MALIHA A ALIKHAN1, CHUNNI LU1, RICHARD KITCHING1,2,5
1Centre for Inflammatory Diseases, Monash University Department of Medicine, Monash Medical Centre, Clayton, Australia, 2Department of Nephrology, Monash Health, Clayton, Australia, 3Burnet Institute, Melbourne, Australia, 4Max-Planck-Institut for Biological Intelligence, Planegg-Martinsried, Germany, 5Department of Paediatric Nephrology, Monash Children’s Hospital, Clayton, Australia
Biography:
Dr. Minh Huan Dang is a nephrologist at Monash Health and Northern Health. He is currently undertaking a PhD at the Centre for Inflammatory Diseases in the Department of Medicine at Monash University and is supported by NHMRC post graduate scholarship. His research focuses on understanding the fundamental mechanism of ANCA-associated vasculitis and defining new therapeutic targets.
Aim:
To define the in vivo pathogenicity of human myeloperoxidase anti-neutrophil cytoplasmic antibodies (hMPO-ANCA).
Background:
While it is accepted that ANCA are pathogenic in ANCA-associated vasculitis (AAV), plasmapheresis is variably effective and there is no direct in vivo evidence of hMPO-ANCA’s pathogenicity.
Methods:
Immunoglobulin G (IgG) fractions were affinity-purified from plasmapheresis effluents of seven patients with MPO-AAV and high titre MPO-ANCA. Reactive oxygen species (ROS) production was assessed from primed human neutrophils stimulated by hMPO-ANCA-containing IgG fractions. Human MPO and human FcγRIIa-expressing mice (hMPO.hFCGR2A mice) primed with lipopolysaccharide and G-CSF were used to determine hMPO-ANCA pathogenicity in vivo.
Results:
Compared with normal human IgG, and after controlling for MPO-ANCA titres, all hMPO-ANCA-containing IgG fractions induced neutrophil ROS production. Some ANCAs were more potent than others, but hMPO-ANCA samples demonstrate similar patterns of responses in neutrophils from three donors. There was no association between ROS production and either hMPO-ANCA IgG subclasses or IgG titres specific for the pathogenic B-cell epitope MPO447-459. Compared with normal human IgG, transfer of hMPO-ANCA (from patient 1) to hMPO.hFCGR2A mice induced intrarenal neutrophil and inflammatory monocyte infiltrates with haematuria and crescentic glomerulonephritis in all recipients, but mice expressing human MPO without human FcγRIIa developed only minimal disease (15.5±1.9% vs 0.4±0.4% crescents, P<0.0001). The three human MPO-ANCAs with the highest MPO-ANCA titres were transferred into hMPO.hFCGR2A mice. While all hMPO-ANCAs induced haematuria and glomerular crescents, severity (including leukocyte infiltrates) varied (MPO-AAV patient 1: 12.6±1.3%, patient 2: 6.6±1.2%, patient 3: 2.0±0.3% crescents, P<0.001; cystatin-C 638.0±30.6, 526.0±31.3, 428.6±24.6μg/L, P=0.0084).
Conclusion:
Human MPO-ANCA induces crescentic glomerulonephritis in vivo and in an FcγRIIa-dependent manner, but the pathogenicity of different hMPO-ANCAs differs in vitro and in vivo.